Froth flotation of ores in the presence of an alpha, alpha-dialkylarylmethyl hydroperoxide



Patented Mar. 13, 1951 2,545,132 FROTH FLOTATION F ORES IN THE rims ENCE OF AN a,a-DIALKYLARYLMETHYL HYDROPER'OXIDE William T. Bishop and Eugene J. Lorand, Wilmington, Del., and John E. Reese, St. Simons Island, Ga., assignors to Hercules Powder Company, Wilmington, Del., a corporation of Delaware- No Drawing. Application June 30, 1948, Serial No. 36,268

7 Claims. (01. 209-166) This invention relates to a process for beneficiating ores and, more particularly, to a process for concentrating ores by froth flotation.

Reagents used in the flotation of ores are of. threegeneral types; namely, frothing agents, collecting agents, and modifying agents. Frothingagents depress the surface tension of the water employed and thus facilitate the formation of air. bubbles when the water isv aerated. Collectors serve to modify the surfaces of the ore particles and cause them to adhere to the air bubbles which-areformedin the water. Modifying agents are used to modify the ore pulp so that the desired minerals be collected into .the froth and the remainder will not. The actionof modifying'agents is supplementary. tothat of the'collectors. This invention comprises a frothflotation process which is carried out in the presence of new frothing agents.

Frothers heretofore employed in the flotation of minerals includepine oil, cresylie acid, cre- ,oisotes, aliphatic alcohols, soaps, and, in a few instances, sul-fonated' organic compounds. For various reasons these reagents have not proved entirely satisfactory. For example, some frothe-rs are characterized by collecting properties'as well as frothing properties or are affected by thecondition of the ore pulp, the pH of the flotation mixture, the presence of other conventional flotation reagents, or a combination of these factors. Furthermore, some frothers exhibit an inhibit= ing reaction on the flotation of the desired mineral. In addition, many desirable frothing agents have been commercially uni'ea'sabie as a consequence of their high cost.

Particularly itdesirable that a frother be characterized by a lack of collecting properties; If a substance possesses bothfrothihg and collection properties, the intensity of one property cannot-be changed with fluctuationsin the ore character without simultaneous changes in the other. property. The result is a very undesirable curtailment in reagent control and a consequent decrease in mill performance in the treatment of complex ores.

Now inv accordance with this invention, ithas been discovered that ores-may be advantageous 'Iy-and economically concentratedby subjecting a pulp or'slurry of the g'rou'ndores to froth flotation in the presence of an organic hydroperoxide. Either 'monoor di-hydroperoxides may beemployed'. The hydroperoxides of thisinventi'on are a;-d1alkylarylmethy1 hydroperoxides.

Them-dialkyl'arylemethyl hydroperoxides' used in accordance with this-invention have the following structural formula in which. R1 and "R2 represent iry-1 gro ps, Ar

a r h me: group xylylene dihydroperoxide. Thesecompounds alsomay be named as aryl(diall;yl ).!ncthy hydroperoxides; for example, a,a-di'meth benz fl hydroperoxide may be designated: as phefiy1(di.- methyl) methyl hydroperoxide. The afr'yl and alkaryl groups need not be derived from benzene,

as is the case in the afore-mentionedgcompounds, for compounds containing aromaticnuclei derived from naphthalene, anthrajcene; phenanthrene, and the like also are operable when disgroups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, secondary butyl, tertiary --butyl and the like, to give alkaryl substituents, the same alkyl groups also being representative of R1 and R2 in the structural formula. R1 and R2 may be either the same or different. These organic hydroperoxides exhibit substantially no collecting properties and are attended-by none ofthe other afore-mentioned disadvantages which characterize the frothers known to the prior art.- These organic hydroperoxides may be used either alone or in conjunction with standard frothers heretofore employed. Likewise, the hydroperoxides may be employed in conjunction with collecting and modifying agents customarily utilized in the flotation art.

Having thus indicated in a general waythe' nature and purpose of this invention, the fol- 1owing examples are offered to illustrate the practice thereof. I All parts are by weight unless otherwise indicated.

Examples I II one thousandtwenty g; of lead ore wasground for 14 minutes in a ball mill with 1'000ml. of

we a X,

solved in a suitable solvent during the oxidation. The aryl group maybe substituted with alkylwater. This ore was composed of galena in a dolomite gangue and contained about 1.2% lead. The ground ore was screened through a 48-mesh screen and the feed transferred to a lD0-g. flotation machine. The pulp was diluted to about solids with water, and 0.15 lb. of sodium sulfide and 0.10 lb. of potassium isopropyl xanthate per ton of ore were added. Then the frothers. listed below were added and a lead conthrough the compounds at a temperature between about C. and about 95 C. in the presence of an aqueous alkali. The concentration of the aqueous alkali may be between about 1% and about although it is preferable to use concentrations of about 2% to about 8%. Vigorous agitation is desirable during the oxidation reaction. The hydroperoxides of this invention can also be prepared by the auto-oxidation of the centrate was removed for 10 minutes. The fol- :0 corresponding hydrocarbons at elevated temlowing results were obtained. perature on irradiation with light of short wave Per Cent Per Cent Per Cent Example Frotlier zg g Leadin gig g Lead Tailing mate Recovery I a, aDimethylbenzyl hydroperoxide l 0. 12 D. 14 46. 9 89. 7 a, a-Dimethyl-pisopropylhenzyl hydroperoxide-l00%. 0. 12 0.17 39.1 87. 3

1 The a, a-dlmethylbenzyl hydroperoxide was however, all but In the beneficiation of minerals by the froth flotation process, the ore or mineral to beconoentrated is first finely ground in the presence of water to the proper particle size for the purpose of liberating the gangue from the metalliferous or mineral components. The ground ma terial is screened to remove the oversized particles. The resultant pulp may then be treated in any of the various types of machines which have been developed for the purpose. Thus, vortex, superaeration, and pneumatic machines of the air-jet type may be employed. Customarily, the value mineral, i. e., the product which it is desired to recover, is floated. However, the procedure may be reversed with the value mineral concentrated in the tailing and the gangue removed in the froth.

Bulk flotation involves the flotation from the ore of a single rough concentrate containing a group of valuable minerals of the ore. Divisional flotation involves a more refined separation of minerals of similar flotation properties from each other, giving a product or number of products each of which contains, in so far as possible, one mineral or only minerals whose presence together is commercially desirable.

The frothing agents of this invention are, of course, operable in both bulk and divisional flotation procedures involving any mineral or ore. Furthermore, these frothing agents are equally advantageous when employed in any of the various types of machines adapted to the processes involved.

The objects of this invention are accomplished prepared by the air oxidation of 6% of the a, a-dimethylbenzyl alcohol and acetophenone Were removed.

by using a,a-dialkylarylmethy1 hydroperoxides as frothing agents in flotation processes for the beneficiation of ores. Such hydroperoxides may be prepared by the oxidation of aIkyl-substituted aromatic organic compounds having the structural formula Ra Ar in which R1 and R2 represent alkyl groups and Ar represents a substituent selected from the group consisting of aryl and alkaryl groups. The oxidation may be carried out in the liquid phase utilizing air or molecular oxygen as the oxidizing agents. A preferred method of preparing these hydroperoxides involves the liquid phase oxidation of the alkyl-substituted aromatic organic compounds having the above structural formula by passing an oxygen-containing gas cumene. In this instance,

length. This method is disclosed in detail by Hook and Lang, Ber. 77, 257-64 (1944). Although all of the organic hydroperoxides embraced by the structural formula previously mentioned are operable, 0.,11 dimethyl p methylbenzyl hydroperoxide, a,a-dimethylbenzy1 hydroperoxide, a,adimethyl p isopropylbenzyl hydroperoxide, a,a,a,a.'-tetramethy1-p-xylylene dihydroperoxide, a. ethyl a methylbenzyl hydroperoxide, (1,11 dimethyl-p-ethylbenzyl hydroperoxide and 11,01- dimethylnaphthylmethyl hydroperoxide are pre-, ferred.

In carrying out this invention the flotation agents comprising an a,a dialkylarylmethyl hydroperoxide may be prepared using several difierent modifications of the hydropercxide material. The hydroperoxide may be used, for example, either in the form of the pure hydroperoxide, or in the form of a crude reaction mixture containing the hydroperoxide and obtained by the oxidation with air or oxygen of an alkylsubstituted aromatic organic compound having the structural formula shown previously. When taining a,a-dimethylbenzyl hydroperoxide, 11,11- dimethylbenzyl alcohol, a small amount of acetophenone, and unchanged cumene. Such a reaction product may be used per se in forming the flotation agents of this invention. In case it is desirable, however, to obtain the hydroperoxide in a more concentrated form, the hydroperoxide may be separated from the other constituents of the crude reaction mixture. The hydroperoxides may be separated from the reaction mixtures by, for example, fractional distillation at very low pressures, of the order of 0.01 to 1.0 mm./sq. cm., the hydroperoxides having higher boiling points than the related hydrocarbon, alcohol and ketone. In some instances the hydroperoxides also may be separated from the oxidation reaction mixtures by crystallization, which may be facilitated by first distilling oif at least part of the hydrocarbon. Steam dis- The oxidation of cumene, for example, leads to'a reaction product contillation usually is sufiicient to remove the hydro carbon.

The organic hydroperoxides of this invention may be utilizedin amounts of from about 0.005 lb. to about 1 lb./ton of ore but. are preferably employed in amounts of from about 0.01 lb.-to about 0.5 lb./ton of ore. In most instances, it is advantageous to employ other flotation agents in addition to the frothers to achieve the most effective separation of the minerals from the ore. These additional froth flotation reagents include collectors and modifying agents.

Collecting agents are chemical compounds which cause the collection of the desired material into the froth. The compounds most commonly employed with metallic sulfide and oxidized metallic ores are the xanthates, dithiophosphates, and diphenyl thiourea. Potassium or sodium ethyl, butyl, and amyl xanthates or mixtures of these are also widely used. The collectors known as dithiophosphates are prepared by the reaction of phosphorous pentasulflde with alcohols or phenols. The most utilized of such compounds are the phosphocresylic acids which contain various percentages of cresylic acid added in excess during the manufacturing process. Sodium salts or" these phosphocresylic acids are also valuable collectors. Likewise, useful collecting agents may be prepared from phosphorous pentasulfide and ethyl, amyl, or butyl alcohols.

In the flotation of nonmetallic ores, fatty acids, fatty acid soaps, and derivatives thereof are most commonly employed as collectors. Typical fatty acids utilized are oleic, stearic, and palmitic. Likewise, soaps comprising the alkali metal salts of these acids are excellent collectors. Sulfonated fatty acids and fatty acid soaps are also widely employed in the art as collecting agents and have the advantage of being more selective in their action.

The organic hydroperoxides of this invention may be efiicaciously and advantageously utilized with any of the various collecting agents hereinbefore mentioned. Furthermore, these hydroperoxides are also operable with other collecting agents known to the art.

Modifying agents are of various types and include pH and pulp control agents, depressing agents, activating agents, sulfldizing agents. dispersing agents, and inhibitors.

The most commonly employed pH and pulp control agents are lime and soda ash for alkaline circuits and sulfuric acid for acid circuits.

Depressing agents include lime, sodium and potassium cyanide, sodium sulfate, sodium sulfite, sodium sulfide, sulfur dioxide, and potassium and sodium dichromate. These compounds are employed both independently and in various combinations.

Copper sulfate, sodium sulfide, and sulfuric acids are used as activating agents for metallic ores. Soluble basic salts of copper, lead, and iron are so utilized in the soap flotation of nonmetallic ores and, as sulfidizing agents, sodium sulfide, hydrogen sulfide, and the various other sulfides and polysulfides of the alkali and alkaline earth metals are employed. agents commonly utilized are sodium silicate, sodium sulfide, citric acid, tannic acid, and lactic acid. Protective colloids, such as starch, glue, gum arabic, casein, gelatin, and the like, are excellent inhibitors.

One skilled in the art of ore beneficiating by froth flotation will be cognizant of the proper collecting and modifying agents to employ to Dispersing obtain the optimum results from'the flotation of a particular ore. The organic hydroperoxides of this invention may be utilized in conjunction with any of the modifying and collecting agents hereinbefore mentioned, either alone or in combination. It is to be understood, however, that the organic hydroperoxides are also operable with any of the various other flotation reagents known to the art.

The frothing agents of this invention may be used generally in the dressing of ores. Sulfide ores, nonsulfide ores, both simple and complex, and nonmetallic ores may be advantageously so treated. Thus, lead, zinc, copper, iron, molybdenum, nickel, and precious metal sulfide and nonsulfide ores may be economically concentrated by froth flotation in the presence of the organic hydroperoxides of this invention. Likewise, mineral ores, such as coal ores, are most eflicaciously beneficiated in the presence of the froth flotation reagents disclosed.

The flotation agents herein disclosed are generally operable for the conditioning of ores or the treating of minerals. However, the conditions most desirable for frothing operations are dependent, in addition to the froth flotation agent, on the size of the ore being treated, the temperature at which the treatment is carried out, the per cent solids in the pulp, and the pH of the flotation mixture. In each case, one skilled in the art will be able to adjust the various con-- ditions to achieve the optimum advantages from the flotation agents employed.

The physical properties of the froth produced. by these organic hydroperoxides are excellent. The froths are composed of fine bubbles which adequately support the weight of the floated mineral, thus facilitating its removal. Further more, the froths do not demonstrate undue stiffness or brittleness but collapse rapidly and completely after the concentrate has been removed- In addition, the froths produced by the hydroperoxides are clean with respect to the fine, slimy gangue which has a tendency to float and contaminate the metallic concentrate.

What we claim and desire to protect by Letters Patent is:

1. In the method of beneflciating ores by froth flotation, the step which comprises aerating a pulp of the ore containing a, collector and from. about 0.01 lb./ton to about 1 lb./ton of the ore of a frother consisting of a substantially purea,a-dialkylarylmethyl hydroperoxide.

2. The process of claim 1 wherein the hydro- T peroxide is a,a-dimethylbenzyl hydroperoxide.

3. The process of claim 1 wherein the hydroperoxide is a,a-dimethyl-p-methylbenzyl hydroperoxide.

4. The process of claim 1 wherein the hydroperoxide is 11,0. dimethyl p isopropylbenzyl hydroperoxide.

5. In the method of beneficiating ores by froth flotation, the step which comprises aerating a pulp of the ore containing a collector and from about 0.01 1b./ton to about 0.5 lb./ton of the ore of a frother consisting of a substantially pure a,a-dialkylarylmethyl hydroperoxide.

6. In the method of beneficiating metalliferous ores by froth flotation, the step which comprises aerating a pulp of the ore containing a collector and from about 0.01 1b./t0n to about 0.5 lb./ton of the ore of a frother consisting of a substantially pure a,c-dialkyl arylmethy1 hydroperoxide.

7. In the method of beneficiatlng coal ores by 8 froth flotation, the step which comprises aerat- UNITED STATES PATENTS ing a pulp of the ore containing a. collector and Number Na e Date from about 0.01 1b./ton to about 0.5 lb./ton of 2 302 462 fi No 17 1942 the ore of a frother consisting of a substantially Palmer No 1942 P fl' y yl y hydroperoxide- 5 2 302 4 3 Palmer 17 942 WHLIAM T. BISHOP. 2,467,369 BlShOp et a1 Apr. 19, 1949 EUGENE LORAN'D OTHER REFERENCES JOHN REESE. Milling Methods, 1930, page 340, Compound 10 172, page 336, Compound 14.

Gaudin Flotation, 1932, McGraw-Hill 00., a es REFERENCES CITED 56 to 62. p g The following references are of record in the Mining hnology, v01. 10, 1946, TP 2011, file of this patent: pages 1 to 6. 

1. IN THE METHOD OF BENEFICIATING ORES BY FROTH FLOTATION, THE STEP WHICH COMPRISES AERATING A PULP OF THE ORE CONTAINING A COLLECTOR AND FROM ABOUT 0.01 LB./TON TO ABOUT 1 LB./TON OF THE ORE OF A FROTHER CONSISTING OF A SUBSTANTIALLY PURE A,A-DIALKYLARYLMETHYL HYDROPEROXIDE. 